Note 5 — THE STORY OF THE UNIVERSE (continued 2)

It is singular that the frog, though so low in the scale of vertebrated animals, should bear a striking resemblance to the human conformation in its organs of progressive motion. This arises from the exertions which it makes in swimming being similar to those of man in walking, in as far as they both result from the strong action of the extensors of the feet. Hence, we find a distinct calf in the legs of both, produced by the swelling of similar muscles. The muscles of the thigh present, also, many analogies with those of man; particularly in the presence of the long muscle called the sartorius, the use of which is to turn the foot outward, both in stepping and in swimming.